1. Field
A perpendicular magnetic recording head is provided. The magnetic recording head performs recording by applying a perpendicular magnetic field to a surface of a recording medium.
2. Related Art
Magnetic heads are classified into a longitudinal recording (in-plane recording) head that performs recording by applying a parallel magnetic field to a surface of a recording medium, and a perpendicular recording magnetic head that performs recording by applying a perpendicular magnetic field to a surface of a recording medium. A perpendicular recording magnetic head is advantageous because of increased recording density.
Generally, a medium-facing surface of a perpendicular magnetic recording head facing a recording medium, a main pole layer and a return path layer are stacked with a nonmagnetic insulating layer disposed therebetween. The main pole layer and the return path layer are magnetically connected in a section at a distance from the medium-facing surface in the height direction. A coil layer is provided in the nonmagnetic insulating layer to apply a recording magnetic field to the main pole layer and the return path layer. When a recording magnetic field is induced between the main pole layer and the return path layer by applying a current to the coil layer, it perpendicularly enters a hard film of the recording medium through a leading end face of the main pole layer exposed from the medium-facing surface, passes through a soft film of the recording medium, and then returns into the return path layer. Magnetic recording is thereby conducted on a portion of the recording medium facing the main pole layer. Perpendicular magnetic recording heads of this type are disclosed in Japanese Unexamined Patent Application Publication Nos. 62-159313, 2001-266310, and 2005-101245.
Recently, the distance between the main pole layer and the return path layer at the medium-facing surface of the perpendicular magnetic recording head; namely, the gap, is commonly set to a small value of approximately 50 nm (shielded pole structure). By adopting such a small gap, magnetic flux that flows from the main pole layer to the return path layer increases, and the inclination of a recording magnetic field, which is emitted from the main pole layer, passes through the recording medium and returns to the return path layer, (magnetic field inclination) increases. This achieves magnetic recording with little fringing. When the magnetic flux that flows from the main pole layer to the return path layer increases, magnetic flux leaking from the main pole layer toward the recording medium is reduced, and the strength of a recording magnetic field decreases. Since the magnetic field inclination increases, the SN ratio is maintained.
When the strength of the recording magnetic field is low, it may be impossible to record on a recording medium having a great coercive force. Moreover, since the writing track width tends to depend on the frequency of a current flowing through the coil layer in the perpendicular magnetic recording head, it is reduced in high-frequency recording. This sometimes reduces and the SN ratio.